Jan. 21, 2011 -- Eating just 1 cup of strawberries or blueberries each week can reduce your risk of developing high blood pressure, a major risk factor for heart disease and stroke. The new findings appear in the February issue of the American Journal of Clinical Nutrition.

The new study included 87,242 women who took part in the Nurses' Health Study II, 46,672 women from the Nurses' Health Study I, and 23,043 men from the Health Professionals Follow-up study. During the 14-year follow-up period, 29,018 women and 5,629 men developed high blood pressure.

Men and women with the highest amount of anthocyanin from blueberries and strawberries had an 8% reduction in their risk for developing high blood pressure, compared to study participants who ate the least amount of these anthocyanin-rich berries, the study showed.

Anthocyanin is a powerful antioxidant that gives blueberries and strawberries their vibrant color. It may also help open blood vessels, which allows for smoother blood flow and a lower risk for high blood pressure.

Berries and Blood Pressure

The risk reduction from eating blueberries and strawberries was most pronounced in study participants who were 60 or younger. The researchers speculate that the reason for this may be that "the cumulative damage over many decades exceeds the capacity for flavonoids to beneficially affect [blood vessel] function and blood pressure in older individuals."

Additionally, the berry connection was not simply due to healthier people tending to eat better. The findings held even after researchers controlled for other factors linked to high blood pressure risk, including family history, body mass index, physical activity, and multiple other dietary factors.

The new study did have its share of limitations. For example, researchers did not measure food intake or blood pressure levels directly. Instead, blood pressure and dietary composition was self-reported by study participants.

Still, "these findings warrant further investigation, including intervention studies designed to test optimal doses of anthocyanin-rich foods for the prevention of hypertension and to underpin guidelines for the prevention and treatment of hypertension," the study authors conclude. They also note that the current results "reinforce the importance of dietary intervention strategies for blood pressure reduction before middle age."